Dental hypersensitivity, especially that arising from dentin and cementum hypersensitivity, is a frequently encountered problem in dentistry and a very troublesome clinical complaint. Hypersensitivity may occur wherever the dentin or cementum of a tooth is exposed by attrition or abrasion, or when the tooth's fine root surface is exposed by periodontal disease. In about 12% of erupted teeth, there is a developmental lack of protective covering of cementum at the cementoenamel junction. As a result, when the exposed dentin is subjected to mechanical, thermal, chemical or osmotic stimuli, the sensory nerves of the teeth become excited and a very painful response results. For example, people with hypersensitive teeth find it very painful to orally ingest certain forms of nourishment, such as liquids or foods that are hot or cold, sweet, hypertonic or contain citric acid. Everyday stimuli such as brushing the teeth may also be painful.
Many attempts have been made to control hypersensitivity of the teeth. For example, U.S. Pat. No. 3,863,006 (Hodosh, M.) describes the use of potassium, lithium or sodium nitrate; U.S. Pat. No. 4,751,072 and U.S. Pat. No. 4,631,185 (both to Kim, S.) describe the use of potassium bicarbonate and potassium chloride; U.S. Pat. No. 4,710,372 and U.S. Pat. No. 4,634,589 ( both to Scheller, H. U.) describe the use of hydroxyapatite or fluorapatite; U.S. Pat. No. 4,057,621 Pashley, D. H., et al.) describes the use of an alkali metal or ammonium oxalate; U.S. Pat. No. 4,415,549 (Shah, N. B.) describes the use of strontium EDTA, fluoride and ammonium glycyrrhizzinate; and, GB990957 (Rosenthal, M. W.) describes the use of strontium for the control of hypersensitivity. The use of strontium ions to treat hypersensitivity was also disclosed in U.S. Pat. Nos. 3,122,483, 3,988,434 and 4,224,310.
However, although clinically the most effective for reducing tooth hypersensitivity, the use of strontium salts for the treatment of hypersensitivity is disliked by patients due to the tendency of strontium salts to leave an unacceptably salty taste or metallic taste in the mouth, even when used in a toothpaste form. Another major disadvantage of strontium dentifrice is the long period of time of application which is required to achieve the clinical effect.
A topical, sustained-release form of an agent capable of controlling dental hypersensitivity could help prevent undesirable taste side effects and still treat the hypersensitive condition. Such a dosage form would be able to release the agent controlling the hypersensitivity at a lower therapeutic level over a long period of time, for example, for weeks. Sustained localized release of the hypersensitivity agent, targeted directly to the hypersensitive site, would also solve the problem of the prolonged time and application currently required to obtain clinical effectiveness with strontium.
Sustained release of an agent to treat a dental disease, peridontal disease, has been reported to be achieved by embedding chlorhexidine in an ethyl cellulose polymer to form a varnish (Friedman, M., et al., J. Perio. Res. 17:323-328 (1982); Friedman, M., et al., IADR Prog. and Abstr. 59:No. 905 (1980); Soskolne, W. A., et al.. J. Perio. Res. 18:330-336 (1983)). This dosage form was also used in the treatment of plaque prevention in patients wearing orthodontic appliances (Friedman, M., et al., J. Dent. Res. 64:1319-1321 (1985)). However, this treatment, termed a varnish because it is applied to the surface of the teeth or tissues, was not deemed useful for the long-term prevention of the dental condition. Thus a need exists for the identification of a varnish composition capable of supplying a dental agent in an efficacious sustained-release, long term dosage form.
Wahmi (U.S. Pat. No. 4,374,824) discloses dentifrices for cleaning and preserving teeth. Disclosed were compositions comprising ginger, magnesium silicate, sodium chloride, catechu, alum, seed and shell of sweet almond, pyrethrum, gum mastic, and tobacco. It was reported that gum mastic was added to the composition to assist in the prevention of tooth decay. The disclosed compositions were intended to be in the form of toothpaste or tooth powders. The Wahmi patent does not disclose the possible long-term anti-hypersensitivity effect of the compositions; further, application of the disclosed compositions two to three times per day is required for antiplaque activity.
Mastic has been used previously for other dental purposes. U.S. Pat. No. 4,668,188 (Wolfenson, G. B.) discloses the use of a curable mastic in the production of an oral impression tray for making impressions of teeth and jaw structures. Mastics have been used in the production of dental molds (U.S. Pat. No. 4,500,288, VonWeissenfluh, H.) and as an adhesive to secure dental articulators (U.S. Pat. Nos. 4,548,581 and 4,382,787, Hoffman, R. E.). U.S. Pat. Nos. 4,532,126 and 4,428,927 (Ebert, W. R., et al.) disclose chewable, filled, one-piece soft elastic gelatin capsules, made chewable by a masticatory substance, such as a synthetic mastic.
U.S. Pat. No. 4,459,277 (Kosti, C. M.) relates to novel plaque compositions for use in evaluating oral hygiene practices. In brief, the patent discloses a water-insoluble, water-immiscible dye emulsified in fine droplets or rupturable capsules. The patent discloses the use of mastic resin as well as alginates, and other gums as an insoluble media for dye dispersion. In particular, sodium carboxymethylcellulose is disclosed. Also disclosed is the possibility of incorporating antibacterial agents such as stannous fluoride into the compositions. Significantly, the Kosti patent is concerned with diagnostic rather than therapeutic applications. The patent fails to suggest compositions exhibiting long-term preventive activity for hypersensitive teeth.
The background art fails to identify any compositions of matter comprising an effective anti-hypersensitivity agent together with a long term sustained release carrier capable of providing efficacious levels of the anti-hypersensitivity agent, either alone or in combination with an adhesive polymer such as a mastic and a plasticizer such as polyethylene glycol, for use as a hypersensitivity preventative by humans and other animals, under conditions in which the anti-hypersensitivity agents have no undersirable side effects such as changes in taste sensations.